A method of LED driver control and apparatus therefor

Abstract

The application discloses an LED driver control method and device, relates to the technical field of LED driving, and is used for making the LED driver work in a wide range of load occasions, aiming at the problem that the high efficiency of the LED driver cannot be guaranteed in different load occasions at present, and providing an LED driver control method, wherein a first controller is used for realizing closed-loop control on a Buck circuit, so that the output voltage of the Buck circuit is stabilized at a set value determined according to a load. In this way, the application needs of different load occasions can be met without closed-loop control on an LLC resonant circuit, the LLC resonant circuit can be kept near a resonant frequency through open-loop control, and the high efficiency is guaranteed. In addition, the efficiency loss caused by the mode of adjusting the Buck circuit instead of the LLC resonant circuit is smaller, so that the overall efficiency of the LED driver is effectively improved in the wide range of load scenes.

Description

An LED driver control method and apparatus Technical Field

[0001] This application relates to the field of LED driver technology, and in particular to an LED driver control method and apparatus. Background Technology

[0002] Most existing light-emitting diode (LED) drivers are implemented through two-stage circuits. The common two-stage circuit has a boost power factor correction circuit (Boost PFC) in the front stage, which regulates the output DC bus through closed-loop control. The DC bus is followed by an LLC resonant circuit. Similarly, the LLC resonant circuit also uses a controller to detect its own output voltage or current to achieve closed-loop regulation, thereby outputting constant current or constant voltage to the LED load.

[0003] Users typically want a driver of the same power rating to be compatible with LED loads of different specifications. Therefore, most LED drivers are designed as constant power drivers, meaning that as long as the output power does not exceed the rated power, the LED driver can be used with multiple different output voltage parameters.

[0004] However, in existing two-stage LED driver designs, if operating under a wide range of load conditions, the operating frequency of the LLC resonant circuit under closed-loop control must also change to adapt to different loads. Therefore, the LLC resonant circuit stage in the LED driver cannot operate at the resonant frequency in all load ranges, and thus cannot achieve high efficiency in any load condition.

[0005] Therefore, those skilled in the art urgently need an LED driver control method to solve the problem that current LED drivers cannot guarantee high efficiency across all load ranges in a wide range of load applications. Summary of the Invention

[0006] The purpose of this application is to provide an LED driver control method and apparatus to solve the problem that current LED drivers cannot guarantee high efficiency across all load ranges in applications with a wide range of loads.

[0007] To solve the above-mentioned technical problems, this application provides an LED driver control method, which is applied to an LED driver including a Buck circuit, a first controller, an open-loop controller and an LLC resonant circuit;

[0008] In this circuit, the Buck circuit serves as the front-end in the two-stage circuit topology of the LED driver and is connected to the LLC resonant circuit. The LLC resonant circuit is connected as the rear-end and connected to the LED load. The input terminal of the first controller is connected to the output terminal of the Buck circuit, and the output terminal of the first controller is connected to the Buck circuit. The open-loop controller is connected to the LLC resonant circuit.

[0009] This method includes:

[0010] The output voltage of the Buck circuit is sampled to obtain the first detection value;

[0011] A first error signal is obtained by performing a proportional-integral operation based on the difference between the first detected value and the preset first reference value.

[0012] The duty cycle or frequency of the switching transistor in the Buck circuit is controlled according to the first error signal so that the voltage output from the Buck circuit to the LLC resonant circuit is stabilized near a set value; wherein, the LLC resonant circuit is controlled by an open-loop controller to operate at a set frequency, which is within a preset range including the resonant frequency of the LLC resonant circuit.

[0013] Preferably, the LED driver further includes a second controller; the input terminal of the second controller is connected to the output terminal of the LLC resonant circuit, and the output terminal of the second controller is connected to the input terminal of the first controller;

[0014] Accordingly, this method also includes:

[0015] The second error signal output by the second controller is obtained; wherein the second error signal is obtained by the second controller through proportional-integral calculation of the difference between the second detection value obtained by sampling the output voltage of the LLC resonant circuit and the preset second reference value.

[0016] Adjust the set value based on the second error signal.

[0017] Preferably, the input voltage of the Buck circuit is a DC voltage of not less than 300V.

[0018] Preferably, the LED driver also includes a rectifier bridge and a Boost PFC circuit;

[0019] The input of the rectifier bridge is connected to an AC power source, the output of the rectifier bridge is connected to the input of the Boost PFC circuit, and the output of the Boost PFC circuit is connected to the input of the Buck circuit to provide a DC voltage of not less than 300V.

[0020] Preferably, adjusting the setpoint based on the second error signal includes:

[0021] The second error signal is superimposed on the first detection value or the first reference value.

[0022] Preferably, superimposing the second error signal with the first detected value or the first reference value includes:

[0023] If the second error signal is negatively correlated with the second detection value, then the second error signal is superimposed on the first reference value;

[0024] If the second error signal is positively correlated with the second detection value, then the second error signal is superimposed on the first detection value.

[0025] To address the aforementioned technical problems, this application also provides an LED driver control device, applied to an LED driver including a Buck circuit, a first controller, an open-loop controller, and an LLC resonant circuit; wherein, the Buck circuit, as the front stage in the two-stage circuit topology of the LED driver, is connected to the LLC resonant circuit; the LLC resonant circuit is connected as the rear stage to the LED load; the input terminal of the first controller is connected to the output terminal of the Buck circuit, and the output terminal of the first controller is connected to the Buck circuit; the open-loop controller is connected to the LLC resonant circuit.

[0026] include:

[0027] The sampling module is used to sample the output voltage of the Buck circuit to obtain the first detection value;

[0028] The calculation module is used to perform proportional-integral calculation based on the difference between the first detected value and the preset first reference value to obtain the first error signal;

[0029] The control module is used to control the duty cycle or frequency of the switching transistor in the Buck circuit according to the first error signal, so that the voltage output from the Buck circuit to the LLC resonant circuit is stabilized near a set value; wherein the LLC resonant circuit is controlled by the open-loop controller to operate at a set frequency, the set frequency being within a preset range including the resonant frequency of the LLC resonant circuit.

[0030] Preferably, the above-mentioned LED driver control device further includes:

[0031] The calibration module is used to acquire the second error signal output by the second controller; wherein the second error signal is obtained by proportional-integral calculation of the difference between the second detection value obtained by the second controller through sampling the output voltage of the LLC resonant circuit and the preset second reference value; and the set value is adjusted according to the second error signal.

[0032] This application provides an LED driver control method applied to a two-stage LED driver topology consisting of a Buck circuit and an LLC resonant circuit. A first controller implements closed-loop control of the Buck circuit, stabilizing its output voltage at different setpoints depending on the LED load. This eliminates the need for closed-loop control of the LLC resonant circuit, meeting the application requirements of various load scenarios. Furthermore, this application also uses an open-loop controller to implement open-loop control of the LLC resonant circuit, ensuring it always operates near its resonant frequency and maintaining high efficiency across all load ranges. Moreover, this approach, which adapts to different loads by adjusting the Buck circuit, results in less efficiency loss than adjusting the LLC resonant circuit, effectively improving the overall efficiency of the LED driver across a wide range of load scenarios.

[0033] The LED driver control device provided in this application corresponds to the above method and has the same effect. Attached Figure Description

[0034] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 shows a circuit diagram of a common LED driver;

[0036] Figure 2 is a circuit structure diagram of an LED driver provided by the present invention;

[0037] Figure 3 is a flowchart of an LED driver control method provided by the present invention;

[0038] Figure 4 is a circuit diagram of a first controller and a second controller provided by the present invention;

[0039] Figure 5 is a control circuit diagram of a Buck circuit and LLC resonant circuit provided by the present invention;

[0040] Figure 6 is a circuit structure diagram of another LED driver provided by the present invention;

[0041] Figure 7 is a structural diagram of an LED driver control device provided by the present invention. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0043] The core of this application is to provide an LED driver control method and apparatus.

[0044] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Currently, common LED drivers, as shown in Figure 1, mostly adopt a two-stage circuit structure. The front stage is a Boost PFC circuit, which regulates the output DC bus through closed-loop control (the closed-loop control part is not shown in Figure 1). The downstream stage of the Boost PFC circuit's DC bus is an LLC resonant circuit, which also adopts a closed-loop control method. The controller detects the output voltage or current of the LLC resonant circuit to perform closed-loop control, thereby achieving constant voltage or constant current output to the LED load to meet the driving requirements.

[0046] In practical applications of LED drivers, it is often desirable for LED drivers of the same power rating to be compatible with LED loads of different specifications, that is, load voltage or current within a wide range. For example, even with the same 100W LED driver, the requirement might be that it can be used with load voltages ranging from 30V to 100V. If only one output voltage parameter is designed, such as 100V / 1A, then the user can only use it with a 100V LED load, which cannot meet the actual application requirements.

[0047] However, if existing two-stage LED drivers are to meet the requirements of operating in a wide range of loads, the operating frequency of the LLC resonant circuit under closed-loop control must also change with the load's voltage and current demands to adapt to different loads. Thus, the operating frequency of the LLC resonant circuit cannot always remain at the resonant frequency. Since the LLC resonant circuit is most efficient at its resonant frequency, and its efficiency decreases significantly further away from the resonant frequency, the LLC resonant circuit stage cannot achieve high efficiency across all load ranges.

[0048] Therefore, in order to solve the above problems, this application provides an LED driver control method, which is applied to the LED driver shown in Figure 2. The LED driver includes: a Buck circuit 11, a first controller 12, an open-loop controller 13, and an LLC resonant circuit 14.

[0049] In this circuit, Buck circuit 11 serves as the front-end in the two-stage circuit topology of the LED driver, and its output is connected to LLC resonant circuit 14; LLC resonant circuit 14 serves as the rear-end, and its output is connected to LED load 15; the input of the first controller 12 is connected to the output of Buck circuit 11, and the output of the first controller 12 is connected to Buck circuit 11; the open-loop controller 13 is connected to LLC resonant circuit 14.

[0050] The method is shown in Figure 3, and includes:

[0051] S11: Sample the output voltage of the Buck circuit to obtain the first detection value.

[0052] The sampling of the output voltage (V1) of Buck circuit 11 can be achieved by a sampling circuit. Considering that the purpose of sampling the output voltage of Buck circuit 11 in this step is to achieve closed-loop control of Buck circuit 11, and the voltage levels of the control branch and the main drive branch are generally different, the sampling circuit can be set according to different ratios of the sampling resistor value to collect the output voltage of Buck circuit 11 according to a certain sampling ratio to participate in closed-loop control. The collected voltage value is the first detection value mentioned above.

[0053] S12: Perform proportional-integral calculation based on the difference between the first detected value and the preset first reference value to obtain the first error signal.

[0054] It should be noted that the implementation method for setting the first reference value can be determined according to the type and model of the first controller 12 actually selected. For example, if the first controller 12 is a microcontroller unit (MCU) or other control device with certain data processing and storage capabilities, the first reference value can be data pre-stored in the control device, or it can be a status value continuously output by other devices. Alternatively, the first controller 12 can be implemented by a simple operational amplifier and its related compensation network, with the compensation network connected between the negative input terminal and the output terminal of the operational amplifier, as shown in Figure 4. In this case, the first reference value needs to be provided by an external device, such as a reference voltage provided by a voltage source as the first reference value.

[0055] Regarding one embodiment of the first controller 12 shown in Figure 4, it should be noted that the compensation network described above is typically a combination of one or more of the following three types: resistor, capacitor, or a resistor and capacitor in series. The operational amplifier described above has two input terminals: one for inputting the first reference value, i.e., connected to a reference voltage source, and the other for inputting the detected value, i.e., connected to the sampling circuit that acquires the output voltage of the Buck circuit 11. Whether the specific positive and negative input terminals of the operational amplifier are connected to the first reference value or the first detected value should be determined based on the logic of the external circuit in the actual application.

[0056] S13: Control the duty cycle or frequency of the switching transistor in the Buck circuit according to the first error signal so that the voltage output from the Buck circuit to the LLC resonant circuit is stabilized near the set value.

[0057] The LLC resonant circuit is controlled by an open-loop controller to operate at a set frequency, which is within a preset range including the resonant frequency of the LLC resonant circuit.

[0058] It is easy to understand that the method provided in this application controls the Buck circuit 11 through a first reference value to stabilize its output voltage near a set value. Therefore, the setting of the first reference value should be adapted to the required set value. The set value corresponds to different load applications. Therefore, for a wide range of LED load 15 driving applications, the required output voltage of the Buck circuit 11 is first determined according to the current load requirements, that is, the set value is determined; then, the corresponding first reference value is determined according to the set value (the sampling ratio affects the first detection value collected, so it also affects the determination of the first reference value for closed-loop control); finally, the first controller 12 realizes the closed-loop control of the output voltage of the Buck circuit 11, and controls the duty cycle or frequency of the switching transistor in the Buck circuit 11 through the output first error signal to stabilize its output voltage near the set value and meet the load driving requirements.

[0059] In addition to using the first controller 12 to perform closed-loop control of the output voltage of the Buck circuit 11 to adapt to different load requirements, this application also uses the open-loop controller 13 to control the operating frequency of the LLC resonant circuit 14, so that the LLC resonant circuit 14 keeps working near the resonant frequency. Under ideal conditions, the open-loop controller 13 can ensure the highest working efficiency by making the LLC resonant circuit 14 work at the resonant frequency. However, since it is difficult to make the parameters of the product completely consistent during the design process and after actual production, it is also difficult to make the operating frequency of the LLC resonant circuit 14 coincide with its resonant frequency when setting it according to the design parameters. Usually, a certain range including the resonant frequency can also ensure high working efficiency.

[0060] The open-loop controller 13 can output a pulse signal with a fixed frequency and a fixed duty cycle to the switching transistor of the LLC resonant circuit 14 as a driving signal for the switching transistor, so that the LLC resonant circuit 14 can operate at a set fixed frequency. When the fixed frequency is set to be equal to or close to the current resonant frequency of the LLC resonant circuit 14, it can be guaranteed that the LLC resonant circuit 14 operates at the maximum efficiency point.

[0061] Furthermore, for the open-loop controller 13 used to output pulse signals with fixed frequency and fixed duty cycle, one possible implementation is shown in FIG5. Specifically, the open-loop controller 13 is a generator that generates fixed frequency and fixed duty cycle.

[0062] Furthermore, the aforementioned fixed frequency and fixed duty cycle can also be generated by multiple different generators, and this embodiment does not impose any restrictions on this. Regarding the implementation of the aforementioned generator, in actual products, a microcontroller or control chip can easily implement the functions of the generator.

[0063] It should also be noted that, in practical implementations, some Buck circuit chips on the market integrate the main switch and driver circuit of the Buck circuit. By simply inputting the aforementioned first error signal at the chip's input terminal, the output voltage of the Buck circuit 11 can be controlled. When the Buck circuit's switch requires a driver circuit, it can be implemented using a switch controller 16, as shown in Figure 5. In this case, the first error signal is the input signal of the switch controller 16. The switch controller 16 generates a corresponding drive signal based on the input first error signal. Different first error signals correspond to drive signals with different frequencies or duty cycles. After the drive signal is input to the Buck circuit 11, it controls the output voltage of the Buck circuit 11 to stabilize at the set value.

[0064] In addition, since there are many types of mature control chips in actual products, all of which have the functions of the aforementioned switch controller 16, namely, changing the frequency or duty cycle of the output drive signal according to the magnitude of the input signal, the Buck circuit 11 with such a control chip does not need to be additionally equipped with a switch controller 16. The first controller 12 can directly input the first error signal into the control chip of the Buck circuit 11.

[0065] For the commonly used Buck circuit control chip, its logic usually requires inputting the first detection value to the negative input terminal of the operational amplifier that constitutes the first controller 12, inputting the first reference value to the positive input terminal of the operational amplifier, and the output terminal of the operational amplifier is the first error signal.

[0066] The LED driver control method provided in this application is based on adjusting the input voltage of an LLC resonant circuit through a Buck circuit and its closed-loop control circuit. This allows the method to adapt to a wide range of different load driving needs without changing the operating frequency of the LLC resonant circuit. The LLC resonant circuit can be kept operating at a set frequency through an open-loop controller. Since the set frequency is within a preset range including the resonant frequency, the LLC resonant circuit operates near its resonant frequency, ensuring the highest possible operating efficiency under different load conditions and better meeting the actual LED load driving requirements. Furthermore, compared to adjusting the operating frequency of the LLC resonant circuit to adapt to different loads, the efficiency loss from adjusting the Buck circuit is less than the efficiency loss from adjusting the LLC resonant circuit's operating frequency, effectively improving the overall efficiency of the LED driver under a wide range of loads.

[0067] As can be seen from the above, the LED driver control method provided in this application is to replace the scheme of closed-loop adjustment of the LLC resonant circuit 14 by using closed-loop control of the Buck circuit 11 to adapt to a wide range of load applications. Under ideal conditions, the LLC resonant circuit 14 can therefore operate at the resonant frequency through the open-loop controller 13 to ensure maximum working efficiency.

[0068] However, it is readily apparent that in actual LED driver applications, the fixed frequency controlling the LLC resonant circuit 14 is determined according to the resonant parameters designed for the LLC resonant circuit 14. However, during the manufacturing process of the LLC resonant circuit 14, the actual resonant parameters are rarely perfectly aligned with the intended resonant frequency, always exhibiting a slight deviation. This means that even with open-loop control of the LLC resonant circuit 14 via the open-loop controller 13, it is difficult to guarantee that the LLC resonant circuit 14 operates precisely at the product's actual resonant frequency, thus failing to achieve maximum efficiency. Furthermore, since this method adapts to a wide range of loads by adjusting the Buck circuit 11 instead of the LLC resonant circuit 14, when the fixed operating frequency of the LLC resonant circuit 14 deviates from the actual resonant frequency, the actual output voltage of the LLC resonant circuit 14 will also deviate from the set voltage. The output voltage setting of the Buck circuit 11 will also be affected, which is detrimental to improving the efficiency of the LED driver.

[0069] Therefore, this embodiment provides a preferred implementation scheme to solve the above problems. As shown in FIG2, the LED driver to which this method is applied further includes: a second controller 17, the input terminal of the second controller 17 is connected to the output terminal of the LLC resonant circuit 14, and the output terminal of the second controller 17 is connected to the input terminal of the first controller 12.

[0070] Accordingly, this method also includes:

[0071] S14: Obtain the second error signal output by the second controller.

[0072] The second error signal is obtained by proportional-integral calculation of the difference between the second detection value obtained by the second controller 17 through sampling the output voltage (Vo) of the LLC resonant circuit 14 and the preset second reference value.

[0073] S15: Adjust the set value according to the second error signal.

[0074] In this embodiment, the second controller 17 acquires the output voltage of the LLC resonant circuit 14 in the same way as the first controller 12 acquires the output voltage of the Buck circuit 11. The voltage can also be sampled through a sampling circuit. Depending on the resistance ratio of the sampling voltage divider resistor, the output voltage of the LLC resonant circuit 14 can be acquired at a certain ratio as needed to obtain the corresponding second detection value.

[0075] Similarly, the specific implementation of the second controller 17 is as shown in Figure 4. Similar to the implementation of the first controller 12 described above, it can be implemented through an operational amplifier and its compensation network. In this case, the second detection value is connected to one of the input terminals of the operational amplifier through a sampling circuit, and the second reference value is provided by a voltage source and connected to the other input terminal of the operational amplifier.

[0076] After the second controller 17 obtains the second detection value, it obtains the second error signal by proportional-integral control through the preset second reference value. The second error signal is used to modify the above-mentioned set value and make fine adjustments based on the closed-loop control implemented by the first controller 12, so that the output voltage of the Buck circuit 11 is more in line with reality.

[0077] That is, the first controller 12 and its control loop are used to stabilize the output voltage of the Buck circuit 11 at the set value so that the LLC resonant circuit 14 can work at the resonant frequency. The second controller 17 and its control loop are used to fine-tune the set value. When there is a deviation between the fixed frequency of the LLC resonant circuit 14 and the actual resonant frequency, the second controller 17 can correct the set value to further ensure the working efficiency of the LED driver.

[0078] Furthermore, this embodiment also provides a possible implementation scheme for adjusting the set value based on the second error signal, wherein step S15 is as follows:

[0079] The second error signal is superimposed on the first detection value or the first reference value.

[0080] As can be seen from the above embodiments, the first controller 12 achieves closed-loop control of the output voltage of the Buck circuit 11 by comparing the first detected value with a preset first reference value, so as to stabilize the output voltage near the set value. Therefore, the set value is related to the first detected value and the first reference value. The set value itself is a virtual parameter and is not actually set in the LED driver. It is used to represent the expected value of the output voltage of the Buck circuit 11 under the closed-loop control of the first controller 12, so as to adapt to different LED loads 15. Therefore, adjusting the set value according to the second error signal is actually adjusting the first detected value or the first reference value according to the second error signal.

[0081] The first detection value is obtained by the first processor through a voltage sampling circuit that collects the output voltage of the Buck circuit 11. Therefore, the set value can be adjusted by directly superimposing the collected "first detection value" onto the "first detection value" received by the first controller 12. The first reference value is similar. As in one possible implementation scheme proposed in the above embodiment, the reference value is provided by a voltage source. In this case, it is inconvenient to adjust the first reference value by replacing the first reference voltage source. Therefore, the first reference value can also be adjusted by superimposing the second error signal onto the output voltage of the first reference voltage source.

[0082] It should be noted that the adjustment of the first detection value can be achieved by changing the sampling ratio of the sampling circuit, but generally the above-described superposition method is used to adjust the set value.

[0083] Furthermore, whether the second error signal is superimposed on the first detected value or the first reference value needs to be determined based on the correlation between the second error signal and the second detected value, that is, based on the connection relationship between the input terminals of the operational amplifier constituting the second controller 17 and the second detected value and the second reference value. Specifically, the above superposition relationship can be divided into two cases:

[0084] 1. If the second error signal is negatively correlated with the second detection value, then the second error signal is superimposed on the first reference value.

[0085] 2. If the second error signal is positively correlated with the second detection value, then the second error signal is superimposed on the first detection value.

[0086] Taking the first scenario as an example, in the specific circuit connection, where the second detected value is input to the negative input terminal of the operational amplifier and the second reference value is input to the positive input terminal, the trend of the second error signal output by the operational amplifier is opposite to the trend of the second detected value. Specifically, when the actual output voltage of the LLC resonant circuit 14 is low, the second detected value is lower than the second reference value. Therefore, the second error signal obtained when the second detected value and the second reference value are input to the negative and positive input terminals respectively will be high. Conversely, if the actual output voltage of the LLC resonant circuit 14 is high, the second detected value is higher than the second reference value, and the second error signal obtained will be low. In other words, the second error signal is negatively correlated with the output voltage of the LLC resonant circuit 14.

[0087] Under the logical relationship determined by this connection, in order to realize the function of the second controller 17 in correcting the set value, the second error signal must be superimposed on the first detection signal when it is input into the first controller 12, so that the second controller 17 can correct the deviation of the output voltage caused by the error between the actual parameters and the design parameters.

[0088] The second case is similar. In this case, the second detection value is input to the positive input terminal of the operational amplifier and the second reference value is input to the negative input terminal. Therefore, the second error signal needs to be superimposed on the second reference value in order to achieve the purpose of correction.

[0089] It should also be noted that when the LED load applied to the LED driver changes, the first and second reference values ​​mentioned above need to be adjusted accordingly to ensure that the LLC resonant circuit 14 operates at the resonant frequency.

[0090] The preferred embodiment provided in this case involves a second controller acquiring the output voltage of the LLC resonant circuit to obtain a second detection value. This second value is then compared with a second reference value, and a proportional-integral control algorithm is used to obtain a second error signal. This error signal is used to adjust the setpoint at which the Buck circuit output voltage is stabilized. Specifically, this means adjusting the first detection value or the first reference value received by the first controller. This can be achieved by superimposing the second error signal onto the original first detection value or the first reference value. Through the correction effect of the second controller, the setpoint can be adjusted according to the actual output voltage of the LLC resonant circuit. This effectively avoids the problem that deviations between design parameters and actual parameters lead to discrepancies between the expected control effect and the actual effect at the beginning of closed-loop control by the first controller. In other words, the closed-loop control of the first controller determines the expected control effect based on the design parameters of each component of the LED driver, aiming to stabilize the Buck circuit output voltage at a setpoint suitable for different loads. The second controller, on the other hand, determines whether there is a deviation between the design parameters and the actual parameters based on the actual output voltage of the LLC resonant circuit. If a deviation exists, the setpoint is corrected to ensure a more reliable control effect.

[0091] As can be seen from the above embodiments, the LED driver control method provided in this application ensures the highest working efficiency by making the LLC resonant circuit work at the resonant frequency. Similarly, in order to improve the overall working efficiency of the LED driver, this embodiment also provides a preferred implementation scheme for improving the efficiency of the Buck circuit level: the input voltage of the Buck circuit is a DC voltage of not less than 300V.

[0092] It is easy to see that when a Buck circuit operates under a high-voltage input environment, for the same power, the Buck circuit handles less current under high-voltage conditions, which is beneficial to reducing the rectification loss of the Buck circuit and improving the efficiency of the Buck circuit stage, thereby improving the overall efficiency of the LED driver.

[0093] In actual engineering implementation, it is relatively difficult to obtain a DC voltage of not less than 300V. Therefore, this embodiment also provides a preferred implementation scheme, as shown in Figure 6. The LED driver mentioned above also includes a rectifier bridge 18 and a Boost PFC circuit 19.

[0094] The input terminal of the rectifier bridge 18 is connected to an AC power supply, the output terminal of the rectifier bridge 18 is connected to the input terminal of the Boost PFC circuit 19, and the output terminal of the Boost PFC circuit 19 is connected to the input terminal of the Buck circuit 11, which is used to provide a DC voltage of not less than 300V.

[0095] The preferred solution provided in this embodiment adds a rectifier bridge and a Boost PFC circuit to the input terminal of the Buck circuit, so that the Buck circuit can achieve a DC voltage input of not less than 300V through AC power supply that is readily available in actual engineering implementation. This allows the Buck circuit to operate in a high-voltage input environment, resulting in a smaller current processed by the Buck circuit, thereby reducing the rectification loss of the Buck circuit and improving the overall efficiency of the LED driver, which better meets the application needs of actual LED load driving applications.

[0096] The above embodiments have described an LED driver control method in detail. This application also provides an embodiment of an LED driver control device. It should be noted that this application describes the device embodiment from two perspectives: one based on functional modules and the other based on hardware.

[0097] From the perspective of functional modules, as shown in Figure 7, this embodiment provides an LED driver control device applied to an LED driver including a Buck circuit, a first controller, an open-loop controller, and an LLC resonant circuit; wherein, the Buck circuit, as the front stage in the two-stage circuit topology of the LED driver, is connected to the LLC resonant circuit; the LLC resonant circuit is connected as the rear stage to the LED load; the input terminal of the first controller is connected to the output terminal of the Buck circuit, and the output terminal of the first controller is connected to the Buck circuit; the open-loop controller is connected to the LLC resonant circuit; including:

[0098] Sampling module 21 is used to sample the output voltage of the Buck circuit to obtain a first detection value;

[0099] The calculation module 22 is used to perform proportional-integral calculation based on the difference between the first detection value and the preset first reference value to obtain the first error signal;

[0100] The control module 23 is used to control the duty cycle or frequency of the switching transistor in the Buck circuit according to the first error signal, so that the voltage output from the Buck circuit to the LLC resonant circuit is stabilized near a set value; wherein, the LLC resonant circuit is controlled by an open-loop controller to operate at a set frequency, and the set frequency is within a preset range including the resonant frequency of the LLC resonant circuit.

[0101] Preferably, the above-mentioned LED driver control device further includes:

[0102] The calibration module is used to acquire the second error signal output by the second controller; wherein the second error signal is obtained by proportional-integral calculation of the difference between the second detection value obtained by the second controller through sampling the output voltage of the LLC resonant circuit and the preset second reference value; and the set value is adjusted according to the second error signal.

[0103] Since the embodiments of the apparatus and the embodiments of the method correspond to each other, please refer to the description of the embodiments of the method for the embodiments of the apparatus, which will not be repeated here.

[0104] This embodiment provides an LED driver control device that samples the output voltage of a Buck circuit using a sampling module to obtain a first detection value. Then, a calculation module compares the first detection value with a first reference value using a proportional-integral control method to obtain a first error signal for subsequent control. Finally, the first error signal is used to control the duty cycle or frequency of the switching transistor in the Buck circuit, so that the output voltage of the Buck circuit can be stabilized near a desired set value. When the set value is based on the current load, the LED driver can meet the load's driving needs without requiring closed-loop control of the LLC resonant circuit. This allows the LLC resonant circuit to always operate at its resonant frequency, resulting in higher efficiency. Furthermore, this method of adjusting the Buck circuit output voltage to adapt to different load conditions results in less efficiency loss compared to adjusting the LLC resonant circuit, thus improving the overall efficiency of the LED driver.

[0105] The above provides a detailed description of an LED driver control method and apparatus provided in this application. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0106] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. An LED driver control method, characterized in that, This invention relates to an LED driver comprising a Buck circuit, a first controller, a second controller, an open-loop controller, an LLC resonant circuit, a rectifier bridge, and a Boost PFC circuit. The Buck circuit serves as the front-end in the LED driver's two-stage circuit topology and is connected to the LLC resonant circuit. The LLC resonant circuit serves as the rear-end and is connected to the LED load. The input terminal of the first controller is connected to the output terminal of the Buck circuit, and the output terminal of the first controller is also connected to the Buck circuit. The open-loop controller is connected to the LLC resonant circuit. The input terminal of the second controller is connected to the output terminal of the LLC resonant circuit, and the output terminal of the second controller is connected to the input terminal of the first controller. The input voltage of the Buck circuit is a DC voltage of not less than 300V. The input terminal of the rectifier bridge is connected to an AC power supply, and the output terminal of the rectifier bridge is connected to the input terminal of the Boost PFC circuit. The output of the PFC circuit is connected to the input of the Buck circuit to provide a DC voltage of not less than 300V. The method includes: sampling the output voltage of the Buck circuit to obtain a first detection value; performing a proportional-integral operation based on the difference between the first detection value and a preset first reference value to obtain a first error signal; controlling the duty cycle or frequency of the switching transistor in the Buck circuit based on the first error signal to stabilize the voltage output from the Buck circuit to the LLC resonant circuit near a set value; wherein the LLC resonant circuit is controlled by the open-loop controller to operate at a set frequency, which is within a preset range including the resonant frequency of the LLC resonant circuit; the set value is based on the LED... The load is determined, and the first reference value is determined based on the sampling ratio of the set value and the first detection value. The method further includes: acquiring a second error signal output by the second controller; wherein the second error signal is obtained by the second controller through proportional-integral calculation of the difference between the second detection value obtained by sampling the output voltage of the LLC resonant circuit and a preset second reference value; adjusting the set value according to the second error signal; wherein adjusting the set value according to the second error signal includes: if the second error signal is negatively correlated with the second detection value, then the second error signal is superimposed on the first reference value; if the second error signal is positively correlated with the second detection value, then the second error signal is superimposed on the first detection value.

2. An LED driver control device, characterized in that, This invention relates to an LED driver comprising a Buck circuit, a first controller, a second controller, an open-loop controller, an LLC resonant circuit, a rectifier bridge, and a Boost PFC circuit. The Buck circuit serves as the front-end in the LED driver's two-stage circuit topology and is connected to the LLC resonant circuit. The LLC resonant circuit serves as the rear-end and is connected to the LED load. The input terminal of the first controller is connected to the output terminal of the Buck circuit, and the output terminal of the first controller is also connected to the Buck circuit. The open-loop controller is connected to the LLC resonant circuit. The input terminal of the second controller is connected to the output terminal of the LLC resonant circuit, and the output terminal of the second controller is connected to the input terminal of the first controller. The input voltage of the Buck circuit is a DC voltage of not less than 300V. The input terminal of the rectifier bridge is connected to an AC power supply, and the output terminal of the rectifier bridge is connected to the input terminal of the Boost PFC circuit. The output terminal of the PFC circuit is connected to the input terminal of the Buck circuit to provide a DC voltage of not less than 300V; it includes: a sampling module for sampling the output voltage of the Buck circuit to obtain a first detection value; a calculation module for performing proportional-integral calculation based on the difference between the first detection value and a preset first reference value to obtain a first error signal; and a control module for controlling the duty cycle or frequency of the switching transistor in the Buck circuit according to the first error signal, so that the voltage output from the Buck circuit to the LLC resonant circuit is stabilized near a set value; wherein, the LLC resonant circuit is controlled by the open-loop controller to operate at a set frequency, which is within a preset range including the resonant frequency of the LLC resonant circuit; The set value is determined based on the LED load, and the first reference value is determined based on the sampling ratio of the set value and the first detection value; the correction module is used to acquire the second error signal output by the second controller; wherein, the second error signal is obtained by the second controller through proportional-integral operation on the difference between the second detection value obtained by sampling the output voltage of the LLC resonant circuit and the preset second reference value; the set value is adjusted according to the second error signal; wherein, adjusting the set value according to the second error signal includes: if the second error signal is negatively correlated with the second detection value, then the second error signal is superimposed on the first reference value; if the second error signal is positively correlated with the second detection value, then the second error signal is superimposed on the first detection value.

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